Ocean Water Chemistry
Dec 22, 2015
Ocean Water Chemistry
Figure 4.17a
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Distribution of Earth’s Water
• Oceans 97.2 %• Ice Caps and Glaciers 2.15 %• Atmosphere 0.001 %• Rivers and Lakes 0.009 %• Inland Seas 0.008 %• Groundwater 0.625 %
Ocean Water is SALTY
• Salinity: Total amount of dissolved solids
•Units: o/oo = 1/1000
•Range: 33 – 37 o/oo
• Increase in salinity:– Increase in Density– Decrease in Freezing Point– Decrease in Vapor Pressure– Increase in Osmotic Pressure
Origin of Salts in Oceans
• Rivers (largest transport of chemicals to ocean)
– Rain + CO2 H2CO3
– Si, Al, Na, K, Mg
• Volcanoes– Cl, S, CO2
• Dust / Rain– Fe, Si
• Anthropogenic– CO2, P
Example Geochemical Cycle
Concept of Steady State
Example 2 Geochemical Cycle
Residence Time(T = Ocean amount/Output rate)
• Concentration of elements in seawater is determined by their removal rate
• Conservative elements:– Major Elements: Cl, Na, SO4, Mg, Ca, K
- Minor Elements: Br, Sr, B, C, F• Non Conservative Elements
– Nutrients: N, P, Si– Dissolved gases: O2, CO2, N2
– Trace Elements: Fe, Al, Mn– Organic Compounds
Residence Time - Concentration
Element Res. Time (yrs)
Na 60 000 000Cl 80 000
000Mg 10 000 000K 6 000 000SO4 9 000 000
Ca 1 000 000Mn 7 000Fe 100
Concentration
Crust (%) Ocean (mg/l)
2.4 10 7700.013 19 5002.3 1 2902.1 3800.026 9054.1 4120.5 0.00022.4 0.002
Dissolved Gases
Gas Solubility:Decreases with Temp. and SalinityIncreases with Pressure
Gases in Atmosphere & Oceans
Percent Gas Phase by Volume
Gas
Atmosphere Surface Ocean Total Ocean
N2 79% 48% 11%
O2 21% 36% 6%
CO2
0.04% 15% 83%
Seawater pH
• Pure water pH = 7• Seawater pH = 7.5 – 8.1• Seawater is very well buffered!
CO2(gas)+H2OH2CO3H++HCO32H+
+CO32
H2O: Universal Polar Solvent
H20: Temperature and Density
H2O: Frozen & Liquid density
H2O: Heat Capacity
• Heat Capacity: heat needed to change the temperature of a substance
• Water has higher heat capacity than:– All solids– All liquids, except liquid ammonia
• Latent heat of Vaporization: heat needed to evaporate a liquid– Water has the highest of all substances
Seawater: Temperature and Density
Seawater: Temperature and salinity
Seawater: Ice Formation
Electromagnetic wave penetration
Open water(low
productivity)
Coastal and Estuarine waters (high productivity)
Nuclear Missile Submarine
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How do we measure light penetration?
Secchi Disc
Water Refraction
Eschrichtius robustus
Sound Velocity
• Influenced by Salinity, Temperature and Pressure– Increases with Salinity– Increases with Temperature– Increases with Pressure
• Concept of Midwater Sound Channel
Study in Detail Fig 5-19!
Sound Channel
Humpback WhalesMegaptera novaeangliae
Gray Whale & Sonar Proposal
Eschrichtius robustus
Gray Whale Migration
Acoustic Pollution